Quiet gear



June 7, 1960 F. E. WEEKS 2,939,331

QUIET GEAR Filed March 25. 1959 idw \L Jl X i 2d if i Fvg. I. 4 4

H/s ATTORNEY United States Patent QUIET GEAR Frank E. Weeks, Boston, Mass., assignor to General Electric "Company, a corporation of New York Filed Mar. 25, 1959, Ser. No. 801,949

5 Claims. (Cl. 74-443) This invention relates to the construction of a quiet gear, and moreparticularly it relates to an improved fabricated gear for reducing the sound-generating vibrations caused by the meshing gear teeth.

Much consideration has been given in the past to the reduction of the noise and undeisrable Vibrations which accompany the meshing of the teeth in a pair of gears. Although the reduction of the noise is desirable for obvious reasons in any piece of machinery employing gears which Iis intended to operate in the vicinity of human beings, the problem has become particularly acute in designing machinery where noiseless and smooth operation is absolutely essential, for example, in the propulsion ,transmission gearing of any marine vessel where a premium is placed on silence.

The phenomenon giving rise to these sound-generating vibrations may be summarized briey as follows. As a pair of meshing gears rotates, the majority of the gear teethV are'free from any imposed stress. At the point where the' gears engage, however, the driving gearA imposes a torque on the driven. gear through contact between the mutually extending gear teeth. In addition to the tangential force which generates the torque imposed on the tooth of the driven gear, and depending upon the type of gear tooth employed, radial force components are also produced. These radial components tend to compress the gear -rim or tire radially toward the hub in one phase ofmeshing and away from the hub in another phase. As successive gear teeth engage and disengage, it will be apparent that a series of periodic compressive impulses are transmitted radially from the tire of the gear to the gearhub. 'I'his energy is transmitted as vibrations from thehub to theV shaft, from the shaft to the bearings, and thence to the supporting structure, where it will appear as'sound, radiated from the large gear casing surfaces and other mechanically or acoustically connected surfaces. i' `Accordingly, aobject of the present invention is to provide an improved fabricated gear having a low noise level in operation. f

Another object is to provide an improved gear for reducing the radiation of sound from a gearunit by reducing the energy of compressive waves travelling from the' gear tire to the hub.

A still further object isvtoV provide an improved gear structure for absorbing and dissipating sound-generating vibrations produced by the meshing teeth of a gear set. Generally stated, the invention is practiced by providingV one or more resilient toroidal members radially spaced between the tire and the hub which act to absorb the compressive vibrations instead of permitting them to travelto the hub.

The' subject matter which is regarded as the invention isfparticularly pointed out vand distinctly claimed in the concluding portion ofV this specification. The invention, however, both as to organization and method of practice, togetherwith further objects and advantages thereof, may hlitlbe understood by reference to the following descrip- 2,939,331 Patented June 7, 19,60v

tion taken in connection with the accompanying drawing,.

Fig. 2 is a cross-section of a modified form of gear employing the invention;

Fig. 3 is a full side view of the modified gear of Fig. 2. Referring now to Fig. 1, the gear structure consists of a hub or journal 1 and a radially spaced gear tire 2. The tire 2 is a cylindrically shaped member and is shownl here as having two rows of gear teeth 2a, 2b disposed on its outer circumferential surface. The shape and disposition of the gear lteeth are not material to an understanding of the present invention, but they may consist either of simple spur gear teeth or preferably, in order to promote smooth and quiet operation, are of the herringbone type. The tire 2 is of relatively rigid construction and is formed with internal radially extending llanges 2c shaped to receive a welding bead and a central annular stiffening rib 2d. Oil retaining rings are attached to the tire 2 at opposite ends and will not be referred to further since they form no part of the present invention.

The journal 1, which acts as a combination gear hub and shaft, is provided with finished surfaces 1a which will be supported by appropriate bearings (not shown) and with radial projections 1b, 1c which form a support structure for the fabricated web and tire assembly.

The web of the gear is a composite structure comprised of radially extending outer ring members 4,- radially extending inner ring members 5, and hollow toroidal shaped members 6 which act `to reflect and dissipate the vibrational energy which would otherwise be transmitted radially inward through the web to the hub. Outer rings 4 are attached to the projections 2c on the tire by a suitable method such as welding and inner rings 5 are similarly attached to the radial projections 1b, 1c on the journal l. The surfaces of the projections 1b, 1c, 2c are so formed that the welds by which the inner and outer rings are attached to these projections fill the space between the members. This interposition of several annular weld areas further reduces the transmitted energy, since it is found that a wave travelling in a solid body will lose a portion of its energy when being transmitted across a boundary between two different materials. The multiple rings of weld metal, being of a slightly different quality than the parent metal, will significantly aid in this dissipation of energy.

Attached between the inner and outer rings by a suitable method such as welding, is the vibration `absorbing and reflecting member 6. As can be seen from the drawing of Fig. 1, member 6 is generally hollow and toroidal in shape and is preferably constructed of a continuous tube of metal having a wall thickness somewhat less than that making up the remainder of the web. The reduced wall thickness acts to give the member more flexibility, relatively speaking, than other portions of the gear structure. A cross-section taken through member 6 illustrates that it is not a circle as would be the case in a true torus, but rather is formed having flattened radially inner and outer surfaces with arcuate sides. This shape increases the radial resiliency of member 6 without signicantly reducing its transverse rigidity, by giving a larger surface area subject to bending in a radial plane. It also provides a flat surface abutting the web portion, which is desirable to facilitate the welding operation. For purposes of convenience of reference herein, member 6 will be referred to hereafter as 'a torus.

Torus 6, as shown here, is preferably formed of seamless tubing bent into aA circular shape, and then flattened .s on 'the radially inner and outer surfaces, for instance by passing through a forming roll. It will beappre'ciated that torus 6 will tend to ex'when opposing forces are applied to it by innerand outer rings 4t and 5. This isdue bothto .the aforementionedfact that torus .6 has a.; smaller Awall thickness, relatively speaking,Y than Ythe other members of theY gear, andV also, due tothe. inherent resiliency provided by the shape of the. torus. .The compressiveV impulse'cting through'the web 4 will pinch or squeeze the torus walls toward 'one anotherY momentarily'and then torus 6., due Vto its resiliency, will spring baclg' to its formershapeA thus rellecting thercomp'ressiye force back towardjthe tire whence itcame. Although a Smallpertion 'ofY the Elementary; impulse. generated. in datering. 4Wi11'befmrmitt d fadiallrinw .web portou, it willibe er'. yf're ucedi-n. magnitude and be dissipated, partly in, traes@ Sion through the @ultime rinas'ufyeldmetal, .Scias to. blend. with .sub- .sequent impulses.' fron! aggressive. gearteeth travelling, through Outer ring.' f4' 'dueV 1.0thefdiscontinuity 'affgrded by torus. 6-

Since @IUS 6315.0. asis.. as a. reflector for the ware energy reaching it through outer ringffi the reected wave will aet to dampen or cancel and thereby reduce subsequenty compressive Waves passing through rings 4 byA interference since the reflected' wave willibe travelling in the opposite direction from the primary wave.

modiled form` ofthe invention may be seen by reference toFig. 2U, in which is shown aV fabricated gear having Va 'more complicated web assembly; The tire section'l) is secured to the hub 11 by three Vaxially s pacedeouter'disks 12; 13 attached to three axially spacedA toriA 14 which in turn are connected' to projections `11a on the hub 11 by three axially/'spaced inner ring members v15. `In order to provideV transverse rigidity and to aid in damping the reflected wave from tori'145`tubular spacer members 16Y are used to axially space the disks 13. In-order to facilitate assembly, smallauxiliary rings 16a.-are-pre-welded to tubular spacers 16 on one end.

These spacer tubesV 16 are located at correspondingY cir. cular-'holes 12a, 13a -which have been cut in ydisks 172, 13" atfequalintervals around the disks-and are secured tothe disks by-a-suitable'means such as welding. Reference to Pig. 3gwill illustrate the location andshape ofv spacer tubes vv16'. Y

Thelr'toroidal `members 1-4 inV Fig.- 2l `function in the same -mannenas the toroidal`v membersg of: Fig. l to absorb -Y the vibrationaly energycimposed upon them by 2,939,3s1` f .f I

heat in the intervening web structure between the torus and the tire. The multiple annular zones of weld metal connecting the web portions to rim, hub, and torus member respectively also have Ya substantial vibration-impeding eect. v

Thus a very simple and effective fabricated gear construction is disclosed which willi-substantially reduce the noise level occasioned by Vthe meshing gear teeth.

Other modiiicationswilloccur to those skilled in the art such as. varyngthe. numbenhpe, andlocationor the vibration' absorbersfwh'i'clrhave. beengshown' inthe preferred embodiments of the invention. For instance, the toroidal member could beof-circular section, rather than the attenedcrossfsection shownl herein. It is, of course, intended to cover inthe appended claims all such modiiications and equivalents which fall within the scope of this invention.

Wha-t I.. Claim .asnew and desreto secure by- Let-ters Patent `of the United 'States is:

1. A quiet gear c omprisinga Cy1ndrialjomnalhavf ing an external radially extending annularangm a gear tire l:la vi 1 1g gear teeth thereon,- coaxially 'spaced from' said iournal'arid'having-an internahradiallr extending. an-

" nular ange, vibration absorbing means securedV at its radially innermost and outermost? surfaces. -to said journal flange .andsaid tire ilangefresp'eetively 'for transmitting torque therebetween, said Yvibration absorbing,y means comprising a hollow toroidal member having, ilexible, walls thinner than the ange members tri-'which iti isse.- cured. v f

2; A quiet gear in accordance withV claim -1':in;whcl1 the vibration absorbing means-comprisesaileXible-walled Y hollow toroidalrmembler with its-inner-andoutergsurfaces1 thef tire lland fthe Vintervening 'web structure. VItV will benotedet-hat-I therfabricated"webY structure, the tire 1.4);` and the hub A1-1 dene twocontinuous---enclosedcavities 17, 18 which are substantially sealed fronrthe outside. YIn-= orde1. tolaid lin'r'edu ci`ng `-the reflectedvibratione voids 17; 1-8.` may be iilledwith. a--suit'able-'sound-deadeuing material by-rneans off'pluggedopenings 4 9; A suitable substancefor.. this purposey consists of Y`a foaming? plastic which.V canY be introduced Vthrough openings -19A and al lowed to expand toV completely lill cavities '17;v 18 with a sound-deadening material whichxis highly effective due tothe largequantity -of gas pockets. 'Theuse of psuch anY absorbingv material will substantially reduce -the er1-V ergyv reflected byntori 14 vand act to dampen and dissipate thislenergy. Y e I'Ihe/operationofy 1rmy--inmproved quietgear willd'be apparent 'from the foregoing description. ASound-gener atingyibrations occasioned byfthe meshinggear teeth' transmit. radiallyl directedV compressive waves. fron-r the tiretcwardzthe hublvorjournal.' Thesecompressive waves.

impinge. upon thegrelatively-resilienttorus 'wallsV which willpfex: ,to reflect andedissipateythe: compressive lfwaves; 'leayingsonly a. small .'.portion ofzfthe'V 'compre"ss'ive.-waves to travelinward (to theshaft -and1:bearings. Due totheisgrellectedfand 'will dissipateaitself :by cancelling -out the ilattenedso that the axialwidth thereoflexceedeits radial dimension. Y i

3. A quiet.gearcomprisingrotatablyhmourrtecljournalr means having Va-radial annular aug'eY disposed-thereon; a gear--tire having gearf-teeth-fthereoncoafxiallyl spaced from saidr journal means andhavingradially'extending.

flange directed inwardlytherefrom, andi afvibr'ationerea atlecting4 member eonnectingthe tireand thejournai`for transmitting .torque therebetween 'and-comprising a con Itinuous hollow toroidal menrber-v havingeaA relatively-#thin wall: and attened-on its-radiallyv innermost andl-outere `most 'surface's'sol as to provide-resiliency in bendingr in:-

the radial direction, whereby radially transmitted com pressive. impulsesv directedjiromthe tireftoftheejournalwill .rbereiectedY back .to-lthe-tire.- f Y 4. quiet gear eomprisingra journal portion includ# ingf aplural-ity. of .radiallyextending;l axially spaced1 joute` .nalv flanges; a= eoaxiallyV disposedfradially.- spaced=tirefpor tionhavingVA gear.A teeth. .thereonfi andfineludingeaiplurality of axially. spaced'. internal; circumferential;angeseequal in: numbereto said journalifanges; a :gpluralityrof: inner web` vrings secured 1 at: their.v innermost peripheriesz tozsaid journalanges; apluralityrorouter websrings securedzattheir outermost peripheries to saidV tire. Vflanges;saidrinner and outer web.,ringsrbeing-radiallyspaced-to; define annularv openingsrcoaxialswith; saidjoumal, andparplui flexibility of the torus, a substantial portion of the energy l .rality of vibration-absorbinghollow toroidal:member-stdinposed in said annular openings andisecuredzto'saidinner. andotltenweb'ringsrfor transmittingtorquetherebetween. each o fsaid toroidal mcmbersgbeing constructed of. ,aleentinuousy hollow tube arrangedtc .ex radiallyfwhemsubv jected to radially Ydireeted,:compressive:impulsenbetween sadfinnerandouter web hereby;Avibrati o11 s .t1'a.ns mined. through: said. cuter gs teethon the. tire .portion ,are-.disspatedfb saidlornidal members. u

5. The combinaticnaccordingito claimt. toroidaljmembier is anannularftube innerandouter surface of thejannulus 'flattenedisohatgthe axialwidth thereof 'exceeds the' radialdituensionjoffthe1 torls,j and the `tire v'and' journalmemberseandfmythe-torus, 'respe'ei tively,Y bytannularweldskwhiclsprovideaaaserieefof lradial4 1y spaced weld nngs between the tire and the ioumal to 1,524,555

increase the impedance `to compressive waves passing 1,648,413

'om the tire to the journal. 2,380,776

References Cited in the le of this patent 5 2,756,607

UNITED STATES PATENTS 52,986 Fryer et al. Mar. 6, 1886 564,514

1,265,811 Ohlson May 14, 1918 859,702

6 Kempton Ian. 27, 1925 Maas Nov. v8, 1927 Miller Y July 31, 1945 Coombes Apr. 10, 1951 Mochel et a1. July 31, 1956 FOREIGN PATENTS Germany Nov. 19, 1932 Germany Dec. 15, 1952 

